1. Field of the Invention
The present invention relates to an electrode material and a method for forming the electrode material.
2. Description of the Related Art
The field of portable electronic devices such as personal computers and cellular phones has progressed significantly. The portable electronic device needs a chargeable power storage device having high energy density, which is small, lightweight, and reliable. As such a power storage device, for example, a lithium-ion secondary battery is known. In addition, development of electrically propelled vehicles on which secondary batteries are mounted has also been progressing rapidly from a rise of growing awareness to environmental problems and energy problems.
In a lithium-ion secondary battery, as a positive electrode active material, a phosphate compound having an olivine structure and containing lithium (Li) and iron (Fe), manganese (Mn), cobalt (Co), or nickel (Ni), such as lithium iron phosphate (LiFePO4), lithium manganese phosphate (LiMnPO4), lithium cobalt phosphate (LiCoPO4), or lithium nickel phosphate (LiNiPO4), has been known (see Patent Document 1, Non-Patent Document 1, and Non-Patent Document 2).
Further, it is proposed that a silicate-based (silicate salt) compound having the same olivine structure as the phosphate compound having an olivine structure be used as a positive electrode active material of a lithium-ion secondary battery (for example, Patent Document 2). Furthermore, in Patent Document 2, a method for increasing conductivity of a positive electrode active material by including a carbon component in the positive electrode active material is disclosed.